マイクロ波放電式中和器の電子引出に関する3次元Hybrid-PIC解析

Abstract

A microwave neutralizer composed of a cylindrical discharge chamber (18 mm in inner diameter) and an L-shaped antenna through which a microwave power of 8W is fed into a working gas was analyzed by a three-dimensional Hybrid-PIC solver to realize the simulation in ion's time/space scale. The microwave heating of electrons was analyzed with another electromagnetic PIC solver, and the obtained microwave power absorption rate was utilized in the Hybrid-PIC solver. Compared with the experimental result, the relative error of the simulated discharge current was about 2%, whereas the error depends on a coefficient in an anomalous resistivity model. The ion density has a peak about 3.34×10(exp 18) per cubic m near the antenna tip, which results in the high ion current (per unit area) into the antenna and the front yoke. Ion number density about 10(exp 18) per cubic m is also kept inside the orifice due to Townsend ionization processes, and it was found that the ions produced near the orifice exit are pushed back toward upstream region due to the potential gradient, and contribute to the electron extraction.